Spark plug



Aug. 22, 1939. A. E. HORNBACK SPARK PLUG Filed April 18, 1958 2 Sheets-Sheet 1 Z I Y i 24 .1; v 2 Z5 Jh drz for: yfr'clz 2E. ffozvzaCk,

Au 22, 1939. A. E. HORNB'ACK 2,170,243

SPARK PLUG Filed April 18, 1938 2 Shee os-Sheet 2 rzzey- Patented Aug. 22, 1939 PATENT OFFICE SPARK PLUG Arch E. Hornback, Chicago, Ill., assignor of onehalf to Owen Van Dyke, J12. Chicago, Ill.

Application April. 18, 1938, Serial No. 202,624

7 Claims. (Cl. 123169) This invention relates to spark plugs for internal combustion engines.

One of the objects of the invention is to provide a spark plug in which the several parts are constructed' and assembled within a shell in such manner that they will not be deleteriously affected by'ignition of gas within the plug or by the combustion of gas in the engine cylinder in which the plug is mounted, and the sparkingldistances between the central and intermediate electrodes and between the intermediate and shell electrodes will be constant.

Another object of the invention is to lessen the cost of production, particularly the cost of the '15 central electrode.

Another featureis the novel construction of the core on the central electrode and the mounting of the intermediate electrode thereon, whereby eflicient sparking isproduced.

Another object is to provide a plug which is quick heating and especially adapted for quick ig nition when the engine is cold.

In the drawings: 9

Fig. 1 is a vertical sectional view, partly in elevation, of a spark plug embodying my invention.

- Fig. 2 is-an enlarged, vertical sectional view of the lower part of the plug shown in Fig. 1.- 4

Fig. 3 is a horizontal section on the line 3-3 of Fig. 2.

Fig. 4 is an enlarged vertical sectional view of the lower part-of a modified form of the invention. Fig. 5 is a horizontal section on the line 5-5 of Fig. 4. Fig. 6 is a view, similar to Fig. 1, showing a mod- .35 ification.

Fig. 7 is a bottom plan view of the plug of Fig. 6.

In that embodiment of the invention shown in Figs. 1 to 3, inclusive, l9 indicates-the shell of the spark plug, screw threaded at H and mounted in a cylinder head l2. The shell I. functions as an electrode. Preferably it is lined with a heat resisting alloy such as nichrcme. An insulating core I3 01 porcelain is mounted in the-shell and surrounds a central electrode M, which is of uniform diameter throughout its length, screw threaded at its upper end to receive the nuts IS, IS, and screw threaded at its lower end to receive the spark conducting disc I! x which is also =threaded and after it has been screwed on said electrode It, the lower end it is upset soas to retain the disc I'l securely in place.

The core 13 has a central bore, the upper portion of which fits snugly around .the central electrode I4, and the lowerportion i9 0! the bore is slightly enlarged, whereby a shoulder 29 is made of heat resisting alloy such asnichrome or formed in the core l3. The central electrode l4 is provided with a horizontal aperture 2| for the purpose of retaining the end of a wire 22 whichis wrapped around the electrode M to form a non-integral shoulder on the said electrode. Pref- 5 erably I; use an asbestos wrapping 23 in combination with the wire 22, said wrapping 23 serving as a packing between the wire shoulder 22 and the shoulder 20 of the core. When the nut I5 is screwed down on the upper end of the electrode 10 M to bear on the core 13, the wire 22 and wrapping 23 on the electrode I! are drawn up against the shoulder 29, whereby the parts are firmly held in assembled relation. A clamp nut 24 fits over the upper part of the core l3 and is screwed into the shell III as indicated at 25, a copper gasket 26 being positioned between the clamp nut 24 and core l3. Another gasket 21 ispositioned between the shell l9 and cor i3, and a gasket 29 is located between the shell l0 and cylinder wall l2.

"I'he means for mounting an intermediate electrode 29 on thecentral electrode i4, between the core i3 and central electrodedisc II, will now be described. The intermediate electrode is indicated at 29 and as shown is in the form of a ring '25 or centrally apertured disc of metal. It may be laminated or solid. An insulating disc 39 of mica is aperturedto fit the central electrode l4 and rests onthe central electrode disc 11. A smaller insulating disc 3i onthe central electrode i4 fills 30 i the space between the intermediate electrode 29 and the central electrode it. Thus the intermediate electrode 29 is insulated from the central of the shell is B", the diameter of the core 32 at its upper end where it abuts the core i3 is 'and at its lower portion, justabove'the intermedi: ate electrode 29, is- The intermediate electrode 29 is also 6" in diameter, and the insulat-' 45 i'ng disc 39 and central electrode terminal ll are each 'in diameter. From this it will be apparent that the gas chamber 33 is in a radial direction at its widest portion and ,4 in its narrowest portion'opposite the intermediate elec- 50 trode 29. The lower edge 34 of the shell Ill is approximately opposite the horizontal center of the intermediate electrode 29. The electrodes. are

other suitable metal. 55

- vention.

The spark gaps between the central electrode disc l1 and intermediate electrode 29 and between the intermediate electrode 29 and the shell electrode l0 remain constant at their predetermined locations and proportions due to the construction described, the selection of materials and the careful proportioning of the several parts, whereby an extraordinarily eflicient sparkplug has been produced.

The elimination of an integral shoulder on the central electrode and the provision of the nonintegral shoulder by means of the wire 22 and asbestos wrapping 23 not only reduces the cost of the electrode by elimination of milling op-- erations, but has the further advantage of providing a slightly resilient bearing for the shoulder 20 of the core i3 which reduces breakage.

In the modification shown in Fig; 4, the several parts, with the exception of the insulating core on which the intermediate electrode 29 is mounted, are the same as those described and shown in Figs. 1 to 3, inclusive. In the modification, said insulating core is made of mica and porcelain instead of mica alone. A porcelain sleeve 35 surrounds the central electrode M from the upper surface of the disc H to the lower end of the core l3. Mica laminations centrallyapertured to fit around the porcelain sleeve 35 are located above and below the intermediate electrode 29, those'between said electrode and the disc l'l being indicated at 36 and those above the intermediate electrode 29 being indicated at 31. The proportions are preferably as heretofore described.

The modified form of plug shown in Fig. 6 is the same as that shown and described in Figs. 1

to 3,;inclusive, excepting that the lower edge 34 of the shell I0 is provided with a pair of stake wires 38. Each of said wires is integral with or rigidly fastened in the lower edge of the shell, extending downwardly a short distance from opposite points on the shell edge as indicated at 39, 39 and then bent to lie in ahorizontal plane and semi-circular form beneath the shell edge but slightly spaced therefrom, each of said wires 38 terminating at the point 49 near the downturned part 39 of the other wire. The horizontal portions of the stake wires are approximately in the same horizontal plane as the intermediate electrode 29. This construction provides a quick heating plug which is especially valuable for frequent cold startings of a motor.

shell, a central electrode mounted in the core, a

second insulating core mounted on the central electrode, and an intermediate electrode mounted on the second insulating core, the, shell having a pair of semi-circular stake wires secured to and spaced from its lower edge, said stake wires being disposed. in a horizontal plane approximately thesame as that of the intermediate electrode.

2. In 'a spark plug having a shell which functions as an electrode, an insulating core in the she'll, a central electrode comprising a shaft of uniform diameter, means on the upper end of the shaft for retaining the core, and a non-integral shoulder formed of slightly compressible material on the shaft, said insulating core being held on the central electrode in contact with said shoulder and said retaining means, said shoulder consisting of a wrapping onthe shaft,

the shaft being apertured to retain the wrapping and prevent movement thereof longitudinally of the shaft.

3. In a spark plug having a shell which functions as an electrode, an insulating core in the shell, a central electrode comprising a. shaft of uniform diameter, means on the upper end of the shaft for retaining thecore, and a non-integral shoulder .formed of slightly compressible material on the shaft, said insulating core being held on the central electrode in contact with said shoulder and said retaining means, said shoulder comprising a wire and asbestos wrapping on the shaft, the shaft being apertured to I retain the wire and prevent movement longitudinally of the shaft.

4. In a spark plug having a shell which functions as an electrode, a central electrode screw threaded at each end, a spark conducting-metal disc screwed on the lower end of the central electrode, the protruding. end of said central electrode being upset against said metal disc for rigidly retaining it, an insulating disc of the same diameter as the metal disc mounted on the central electrode above the metal disc, an insulating sleeve of smaller diameter than the insulating disc mounted on said central electrode above said disc, a metal ring constituting an 3 tions asan electrode, an insulating core' in the shell, a central electrode mounted in the core, a second insulating core mounted on the central electrode, and an intermediate electrode mounted on the second insulating core in a plane slightly below the lowerend of the shell and slightly above the lower end of the central elec trode, said central electrode terminating at its lower end in a spark conducting disc 95.," in diameter, the intermediate electrode being 1 5."

'in diameter, that part of the insulating core between said disc and intermediate electrode being 96, in diameter and that part' above the intermediate electrode being e 5" in diameter, gradually diminishing to {5" diameter'at its upper end, and the internal diameter of the shell being i%'', whereby a restricted gas chamber is formed between said shell and said insulating core and electrode mounted thereon.

6. A quick heating spark plug comprising a shell which functions as an electrode, an insulating core mounted in the shell, the lower end of the core being spaced from the shell, a central electrode mounted in the core, a concentric disc on the lower end of the central electr0de,-a second insulating core slightly spaced from. the shell and. mounted on the central electrode between said disc and first mentioned core, and a concentric ring which functions as an intermediate electrode mounted on the second insulating core in a plane slightly below the lower end 'of the electrodes, being continuous circumferentially lating core mounted and the space between the shell and said cores providing an airchamber within the shell having a restricted passage between the lower end of the shell and the second insulating core.

'l. A quick heating spark plug comprising a shell which functions as an electrode, an insuof the core being spaced from the shell, 9. central electrode mounted in the core, a concentric disc on the lower end of-the central electrode, a second insulating core slightly spaced from the shell and mounted on the central electrode between said disc and first mentioned core, and a concentric ring which 1 ctions as an intermediate electrode mounted on the second insulating core in the shell.,the lower end the second insulating core. ARC

in a plane slightly below the lower end of the shell and slightly above the disc ofthe central electrode, said second insulating core being made of mica, and being of the same diameter as the intermediate electrode ring in that portion immediately above diameter, equal to the disc on the central electrode, in that portion between the ring and disc, the spark gaps between proximate electrodes being continuous circumferentially and the space between the shell and said cores providing an air chamber within the shell having a restricted passage between the lower end of the shell and H E. HORNBACK.

the ring, and of smaller 

